Garduño J, García JJ. Nickel-Catalyzed Transfer Hydrogenation of Benzonitriles with 2-Propanol and 1,4-Butanediol as the Hydrogen Source.
ACS OMEGA 2017;
2:2337-2343. [PMID:
31457582 PMCID:
PMC6641154 DOI:
10.1021/acsomega.7b00545]
[Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 05/16/2017] [Indexed: 06/10/2023]
Abstract
The homogeneous transfer hydrogenation of benzonitrile with 2-propanol or 1,4-butanediol produced N-benzylidene benzylamine (BBA, 85% yield) using 5 mol % [Ni(COD)2] as a catalytic precursor and a mixture of Cy2P(CH2)2PCy2 and Cy2P(CH2)2P(O)Cy2 as ancillary ligands, under mild reaction conditions (120 °C, 96 h, tetrahydrofuran). 1,4-Butanediol performed better than 2-propanol as a hydrogen donor and yielded γ-butyrolactone as the product of transfer dehydrogenation. Selectivity toward dibenzylamine (DBA, 62% yield) was achieved by varying the amount of 1,4-butanediol in the catalytic system. A reaction mechanism was proposed, involving a ligand-assisted O-H bond activation, end-on substrate coordination, and a key dihydrido-Ni(II) intermediate, leading to the in situ formation of primary imines and amines to ultimately yield the secondary imines observed.
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